The present invention relates to data set diagnostic systems.
The communication of high-speed data over voiceband telephone lines, for example, requires the use of so-called data sets, or modems. The principal function of a data set is to modulate user-provided data into the passband of the telephone line at the transmitting end and demodulate the received data signals out of the passband at the receiving end and recover the user-provided data.
Recently, networks of data sets have been provided with so-called diagnostic capability, in which the data sets and, in some networks, separate diagnostic control devices, communicate with each other via, for example, a narrow bandwidth "secondary" channel within the passband of the telephone line. For example, a control device--such as a diagnostic control device or a control data set--may transmit a "text" to a "downstream" device, such as a tributary data set, instructing it to perform a particular test or to change an option under which the tributary data set operates. The latter, in turn, will perform the action required and return to the upstream control device a text embodying the results of the test or other indication relative to the requested action.